This invention relates generally to air distribution systems and more particularly to a system powered terminal unit that is controlled by central electronic control equipment.
The heating and cooling of buildings such as large office buildings is typically achieved by heating or cooling air and passing the conditioned air through ventilating ducts leading to the separate offices or other areas of the building. It is highly desirable to provide individual temperature control for the separate areas of the building, and this is normally accomplished by equipping each duct or air diffuser with a flow control device. By providing individual control of each flow control device, the volume of conditioned air flowing into each area of the building can be separately controlled. Air distribution systems of this type are generally high in efficiency and low in cost since they can utilize a single large heating or cooling unit to supply several rooms or floors of the building. At the same time, there is no sacrifice in the individual temperature control for each office.
U.S. Pat. No. 4,312,475 to Edwards et al discloses a variable air volume terminal unit that has significant advantages over other system powered units. In addition to the benefits set forth in the patent, the casing of the terminal unit forms an extension of the trunk duct system, thereby eliminating the need for run out ducts and the attendant pressure losses. The duct system thus has a lower initial cost and, perhaps more importantly, the duct design can be optimized to reduce the system static pressure by at least one half inch W.G. The terminal unit itself requires about one half inch W.G. less pressure than other known terminals. The overall result is that the fan static pressure requirements are reduced by about one inch W.G. which amounts to an energy saving of approximately ten percent of the total energy cost of a typical office building. The primary disadvantage of system powered terminal units has been that there is a lack of communication between them and other parts of the air distribution system. Consequently, conditions in other areas of the building are not taken into account in controlling the terminal unit.
An electronic control circuit for regulating the heating and cooling of a building is shown in pending U.S. patent application Ser. No. 328,112 abandoned, filed on Dec. 7, 1981 by Ken Aubrey. The central control provided by this type of energy management system permits the building HVAC system to be monitored and controlled from a single central location. A readout can be provided for the temperature in each zone of the building, and the temperatures can be reset from the control console individually in each zone or collectively for all zones on either a daily or weekly basis. Consequently, energy consumption can be minimized by heating and cooling the building only when and where necessary. Energy is further conserved since outside weather conditions can be monitored and taken into account in initiating the heating or cooling at the proper time to achieve the desired building temperature when people begin to arrive in the building. The total electrical load can be limited to create additional energy savings.
An electronic energy management system can also save on maintenance costs by reducing the time and labor involved in trouble shooting the equipment. When a monitored condition departs from a preset range, the system provides a warning which pinpoints both the problem and its location so that corrective measures can be taken before a serious equipment failure occurs. The need for servicemen and the time required to investigate problems are thus significantly reduced, as is the down time of the equipment. In addition to temperatures, electronic systems can easily monitor other conditions such as fire. The presence of a fire can be detected by suitable smoke or fire detectors, and the flow of conditioned air to the floor of the fire can be shut off while the air flow can be maximized to other floors. This results in pressurization of the areas around the fire to help contain it and to prevent smoke from spreading, as increasingly required by modern fire codes.